Even the last 2 weeks, the difference has been staggering. At the time of writing we're at 58% Elyos to 42% Asmo, this is not ok.
The fact that people are leaving for their own personal reasons and issues is more of a personal thing and their feelings about how this server is being handled, but those are only a few percent. A lot of people here are playing for nostalgia or just playing what is know as one of the better of Aion's patches. They want to have people to play with, they want both pve and pvp and this requires people. Anyone looking to join the server who sees the faction imbalance is either going to look for another server or just join Elyos because no one wants to be on the 'losing' side.
Asmodians have always been the underdogs, but this didn't always mean they were 'losing'. For some it doesn't matter, but after playing a desolate p2w retail server or a server with 20 people, players want to see other players.
I know I'm part of the problem too. For 8 years I was Asmodian and for the first time in my Aion history, I chose Elyos on this server purely for the fact that the faction isn't dying (yet). I wanted to play Asmodian, but why would I? High ranks are leaving, no one bothers with alliances in seiges, the chances of being zerged when doing dailies is higher, trying to get groups together to pvp or even to pve is exponentially more difficult. Why would I want to struggle when I want to have fun?
Block Elyos character creation and give Asmodians TRUE incentives. Give them pvp buffs, seige buffs, pvp gear at 50, or even a large chunk of BM's or AC's at 65 to get them started. Give them a permanent mount, or a 30days boost pack. Give them 100% exp boost 100% of the time and 200% on weekends, ANYTHING to get people to play or at least give some of the Elyos a reason to reroll if a faction change ticket isn't possible.
Something needs to be done and it needs to be done soon. I for one would roll back to Asmodian given the right opportunity.